A DC-DC converter is an electronic circuit that converts a source of direct current (DC) from one voltage to another. For example, DC-DC converters are widely used in portable devices to provide power from a battery. DC-DC converters may also regulate the output voltage, compensating for varying load current and variations in the input voltage.
FIG. 1A illustrates one common type of DC-DC converter. The DC-DC converter circuit 100 in FIG. 1A (simplified to facilitate illustration and description) is a switching step-down converter (the input voltage is higher than the output voltage), and the basic design is called a Buck converter. In FIG. 1A, a power source 102 provides direct current at an input voltage VIN. The circuit 100 provides direct current to a load (RLOAD) at an output voltage VOUT. Two electronic switches (SW1, SW2) are controlled by a switch control circuit 106 and driver 108. At most only one switch is closed at any one time. When SW1 is closed, current from the source 102 flows into RLOAD and a filter capacitor (C), and VOUT rises linearly. In addition, when SW1 is closed, energy is stored in L and C. When SW2 is closed, current flows from stored energy in C and from stored energy in L, and VOUT decreases linearly. A comparator 104 compares VOUT to a reference voltage VREF, and the switch control circuit 106 adjusts the duty cycle of SW1 in response to the output of comparator 104.
There are many variations in topology and control of DC-DC converters. The circuit illustrated in FIG. 1A has a single inductor. There are variations, for example, LLC, with multiple inductor resonant circuits. The circuit illustrated in FIG. 1A uses output voltage feedback. Some circuits use current feedback. Some circuits have multiple feedback loops.
In general, there is a need to verify operation of a DC-DC converter (design testing, production testing, and system testing), and, in general, there is a need for improving efficiency.